1. Technical Field
The present invention relates to a surface mount type crystal oscillator (hereunder, referred to as a “surface mount oscillator”), and in particular, to a communication terminal (such as a crystal inspection terminal and a writing terminal) of a surface mount oscillator with reduced height.
2. Background of the Invention
A surface mount oscillator, because of its small size and light weight, is used particularly in portable electronic devices as a source of frequency reference or time reference. As an example of this, there has been proposed a surface mount oscillator for an electronic card that includes, for example, a SIM (subscriber identity module) card in which a crystal piece and an IC chip are arranged in parallel in the horizontal direction.
3. Prior Art
FIG. 3 is a drawing for describing a conventional example of a surface mount oscillator, wherein FIG. 3A is a broken sectional [sectional] view, and FIG. 3B is a plan view with a metal cover removed.
A surface mount oscillator of the conventional example is such that a crystal piece 2 and an IC chip 3 are housed within a concave section of a container main body 1 with a frame wall 1b laminated on a bottom wall 1a made of a ceramic material, and a metallic cover 4 covers them to thereby seal-enclose them therein. The container main body 1 is of a sectionally concave shape, and is made of laminated ceramics having a rectangular shape in plan view. On the inner bottom surface 1d of the container main body 1, there are provided a pair of crystal retention terminals 5 and circuit terminals 6 of the IC chip 3, and on the outer bottom surface 1f thereof, there are provided mount terminals 7 that correspond to a set substrate to be equipped together with other electronic components.
Here the crystal piece 2 is of a rectangular shape in plan view, and is AT cut for example. Moreover, on both principle surfaces of the crystal piece 2, there is provided an excitation electrode 8, and lead-out electrodes 9 extends out from both sides of one lengthwise end section thereof. The both sides of the one end section of the crystal piece 2, from which the lead-out electrodes 9 extend out, are fixed to the crystal retention terminals 5 by means of an electrically conductive adhesive agent 10. The IC chip 3 has an integrated amplifier and the like that configure an oscillating circuit, and is arranged on the inner bottom surface 1d of the container main body 1 so as to be adjacent to and horizontally parallel with the crystal piece 2. Moreover, it is flip-chip bonded using bumps 11, and respective IC terminals (not shown in the drawing) provided on the circuit forming surface are electrically connected to the circuit terminals 6 provided on the inner bottom surface 1d. 
The crystal terminals among the IC terminals are electrically connected to the crystal retention terminals 5, and a power supply terminal, a ground terminal, an output terminal, an AFC terminal, and the like among the IC terminals are electrically connected, via end surface electrodes 7a, which are formed by means of through-hole processing, to the mount terminals 7. The metallic cover 4 is joined onto a seam ring 12 provided on an opening end surface 1e of the container main body 1, by means of seam welding for example. The seam ring 12 is made of a metallic body or a thick metallic film.
In such a conventional surface mount oscillator, the crystal piece 2 and the IC chip 3 are arranged in parallel in the horizontal direction on the inner bottom surface 1d of the container main body 1. Therefore, it is possible to reduce the height thereof, compared to one in which the IC chip 3 is arranged under, that is to say, arranged vertically-superimposed under the lower surface of the crystal piece 2, both sides of one end section of which are fixed on an inner wall step section as shown in FIG. 4 for example. As a result, it is suitable as a surface mount oscillator to be built-in in a thin electronic device or even in an electronic card.
Incidentally, in a case where the crystal piece 2 and the IC chip 3 are arranged in parallel in the horizontal direction on the inner bottom surface 1d, the height of the container main body 1 may be approximately 0.3 mm and the thickness of the metallic cover 4 may be 70 μm; and in a case where the seam ring 12 provided on the opening end surface 1e of the container main body 1 is a metallic body (120 μm), the total height may be approximately 0.5 μm; and moreover in a case where the seam ring 12 is a thick metallic film (film thickness 10 to 20 μm), the height may be approximately 0.4 mm.
On the other hand, in a case where the crystal piece 2 and the IC chip 3 are arranged vertically superimposed, the height of the container main body 1 is 0.55 mm. Moreover, with the thickness of the seam ring 12 (metallic body: thickness 120 μm) and the metallic cover 4 (thickness 70 μm), the total height thereof is approximately 0.75 mm. Therefore, in a case where the crystal piece 2 and the IC chip 3 are arranged in parallel in the horizontal direction, the height of the entire oscillator can be reduced. (refer to Japanese Unexamined Patent Publication No. H09-83248, and Japanese Unexamined Patent Publication No. 2006-13650)